Ch 17: Autonomic Division of NSCh 17: Autonomic Division of NS

Compare and contrast the structures of the Compare and contrast the structures of the sympathetic and the parasympathetic sympathetic and the parasympathetic divisions, including functions and divisions, including functions and neurotransmitters.neurotransmitters.

Show the levels of integration in the ANS, and Show the levels of integration in the ANS, and compare these with the SNS.compare these with the SNS.

Overview of ANSOverview of ANS

Pathway for Visceral Motor Output Pathway for Visceral Motor Output

ANS has two antagonistic divisions:ANS has two antagonistic divisions:

1.1. SympatheticSympathetic

2.2. ParasympatheticParasympathetic

ANS output always involves two neurons ANS output always involves two neurons between spinal cord (CNS) and effector.between spinal cord (CNS) and effector.

Synapsing takes place in Synapsing takes place in gangliaganglia

Naming of neurons:Naming of neurons:

neuron #1neuron #1

preganglionic preganglionic

presynaptic presynaptic

neuron #2neuron #2

GanglionicGanglionic

postsynapticpostsynaptic effectoreffector

Preganglionic fiber (=axon):Always myelinated

Postganglionic fiber:Always unmyelinated

Fig 17.3?

Sympathetic DivisionSympathetic DivisionThoracolumbar divisionThoracolumbar division

Preganglionic neurons (cell bodies) located between T1 Preganglionic neurons (cell bodies) located between T1 & L2 of spinal cord& L2 of spinal cord

Ganglionic neurons (cell bodies) in ganglia near vertebral Ganglionic neurons (cell bodies) in ganglia near vertebral columncolumnParavertebral gangliaParavertebral ganglia = sympathetic chain ganglia = sympathetic chain gangliaPrevertebral gangliaPrevertebral ganglia = collateral ganglia = collateral ganglia

Special case: adrenal medullaSpecial case: adrenal medulla

Effects of Sympathetic Division?Effects of Sympathetic Division?

Special Case: Adrenal medullaAdrenal medulla

Fig. 17-6

Modified sympathetic ganModified sympathetic ganglionglion

Terminus for neuron #1, stimulates specialized Terminus for neuron #1, stimulates specialized 2nd order neurons with very short axons in 2nd order neurons with very short axons in adrenal medulla to release NT into blood stream adrenal medulla to release NT into blood stream (= hormones)(= hormones)

Epinephrine (adrenalin) ~ 80% and Epinephrine (adrenalin) ~ 80% and norepinephrine (noradrenalin)norepinephrine (noradrenalin)

Endocrine effects are longer lasting than nervous Endocrine effects are longer lasting than nervous system effects system effects

Sympathetic Sympathetic Neuroeffector Neuroeffector

JunctionsJunctions

Fig 17-6

Differ from somatic Differ from somatic neuromuscular neuromuscular junctionsjunctions

VaricositiesVaricosities

Summary of Sympathetic DivisionSummary of Sympathetic Division

A. Neuron #1 is short, neuron #2 is longA. Neuron #1 is short, neuron #2 is long

B. Synapsing occurs in prevertebral chain ganglia or B. Synapsing occurs in prevertebral chain ganglia or paravertebral collateral gangliaparavertebral collateral ganglia

C. Neuron #1 releases Ach, usually neuron #2 C. Neuron #1 releases Ach, usually neuron #2 releases NEreleases NE

D. Prepares for emergency action, excitatory to D. Prepares for emergency action, excitatory to many organs, inhibitory to others ( digestive for many organs, inhibitory to others ( digestive for example)example)

E. Effects very widespread and somewhat persistentE. Effects very widespread and somewhat persistent

Para – SympatheticPara – SympatheticDivisionDivision

CraniosacralCraniosacral division division

Preganglionic neurons (cell bodies) Preganglionic neurons (cell bodies) located in brain stem & sacral segments of located in brain stem & sacral segments of spinal cordspinal cord

Ganglionic neurons (cell bodies) in ganglia Ganglionic neurons (cell bodies) in ganglia near target organs: near target organs: Intramural gangliaIntramural ganglia

Effects of parasympathetic division ?Effects of parasympathetic division ?

Summary of Parasympathetic DivisionSummary of Parasympathetic Division

A. Neurons #1 are long, come from the A. Neurons #1 are long, come from the brain stem or sacral spinal cord, run brain stem or sacral spinal cord, run with the spinal or pelvic nerves and with the spinal or pelvic nerves and produce ACh. produce ACh.

B. Neurons #2 are short, produce ACh, B. Neurons #2 are short, produce ACh, and may be either excitory or and may be either excitory or inhibitory.inhibitory.

Anatomy of Dual InnervationAnatomy of Dual Innervation

Each organ receives Each organ receives innervation from innervation from sympathetic and sympathetic and parasympathetic fibersparasympathetic fibers

Fibers of both divisions meet Fibers of both divisions meet & commingle at plexuses & commingle at plexuses (fig 17-9) to innervate (fig 17-9) to innervate organs close to those organs close to those centerscenters

Names of plexuses derived Names of plexuses derived from locations or organs from locations or organs involvedinvolved